U.S. patent number 8,550,199 [Application Number 13/148,635] was granted by the patent office on 2013-10-08 for bicycle transmission system.
This patent grant is currently assigned to Nexxtdrive Limited. The grantee listed for this patent is Frank Moeller, Martin Weber. Invention is credited to Frank Moeller, Martin Weber.
United States Patent |
8,550,199 |
Moeller , et al. |
October 8, 2013 |
Bicycle transmission system
Abstract
A method is provided for controlling operation of a pedal cycle
(10) having a rear hub-mounted electro-mechanical transmission
arrangement in which a chain-driven rear sprocket (80), an input
electrical machine (120) and the hub (100) are each coupled to a
respective branch of a three-branch epicyclic gear set (140).
Allowing for natural variations in input torque by a cyclist over a
cycle of the crank arms (50), a substantially constant current is
caused to exist in the input electrical machine (120) such that a
change in torque applied by the cyclist results in a change in
transmission ratio between the rear sprocket (80) and the hub
(100), thereby providing a form of automatic and continuously
variable transmission for the pedal cycle (10).
Inventors: |
Moeller; Frank (Milford,
GB), Weber; Martin (Berlin, DE) |
Applicant: |
Name |
City |
State |
Country |
Type |
Moeller; Frank
Weber; Martin |
Milford
Berlin |
N/A
N/A |
GB
DE |
|
|
Assignee: |
Nexxtdrive Limited (London,
GB)
|
Family
ID: |
40548103 |
Appl.
No.: |
13/148,635 |
Filed: |
February 12, 2010 |
PCT
Filed: |
February 12, 2010 |
PCT No.: |
PCT/GB2010/000249 |
371(c)(1),(2),(4) Date: |
October 05, 2011 |
PCT
Pub. No.: |
WO2010/092345 |
PCT
Pub. Date: |
August 19, 2010 |
Prior Publication Data
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|
|
|
Document
Identifier |
Publication Date |
|
US 20120012412 A1 |
Jan 19, 2012 |
|
Foreign Application Priority Data
|
|
|
|
|
Feb 12, 2009 [GB] |
|
|
0902356.5 |
Apr 24, 2009 [EP] |
|
|
09251183 |
May 5, 2009 [EP] |
|
|
09159467 |
|
Current U.S.
Class: |
180/206.3;
180/206.7 |
Current CPC
Class: |
B62M
6/55 (20130101); B62M 11/14 (20130101); B62M
6/65 (20130101); B62M 11/145 (20130101); B62M
6/45 (20130101); H02K 7/116 (20130101); B60L
50/20 (20190201); B60L 2200/12 (20130101); Y02T
10/646 (20130101); B60L 2240/421 (20130101); Y02T
10/64 (20130101); B60L 2220/42 (20130101); B60L
2240/486 (20130101); Y02T 10/641 (20130101) |
Current International
Class: |
B62M
6/50 (20100101) |
Field of
Search: |
;180/206.1,206.2,206.3,206.7 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
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|
19949225 |
|
Apr 2001 |
|
DE |
|
10243751 |
|
Jun 2003 |
|
DE |
|
102007050552 |
|
Sep 2008 |
|
DE |
|
0937600 |
|
Aug 1999 |
|
EP |
|
09251183.1 |
|
Aug 2010 |
|
EP |
|
04321482 |
|
Nov 1992 |
|
JP |
|
10203466 |
|
Aug 1998 |
|
JP |
|
2002331984 |
|
Nov 2002 |
|
JP |
|
2008285069 |
|
May 2007 |
|
JP |
|
00/43259 |
|
Jul 2000 |
|
WO |
|
00/59773 |
|
Oct 2000 |
|
WO |
|
2006035215 |
|
Apr 2006 |
|
WO |
|
Other References
PCT International Search Report and Written Opinion for
PCT/GB2010/000249 dated May 18, 2010. cited by applicant .
GB Search Report for Application No. GB0902356.5 dated May 6, 2009.
cited by applicant .
EPO Extended Search Report for Application No. 09159467.1 dated
Apr. 16, 2010. cited by applicant .
EPO Extended Search Report for Application No. 09251183.1 dated
Mar. 29, 2010. cited by applicant.
|
Primary Examiner: Hurley; Kevin
Attorney, Agent or Firm: Ahn; Harry K. McCarter &
English, LLP
Claims
The invention claimed is:
1. A method of operating a pedal cycle, the pedal cycle having an
electro-mechanical drive arrangement including an input electrical
machine, an output electrical machine and an input epicyclic gear
set; wherein, of the input epicyclic gear set, a first component is
coupled to be driven by crank arms of the cycle, a second component
is coupled to one of the rotor and stator of the input electrical
machine, the other of the rotor and stator being fixed relative to
the cycle, and the third component is coupled to drive a wheel of
the cycle; the output electrical machine being arranged to at least
assist in driving the or another wheel of the cycle when operated
as a motor; the method including the steps of: a) operating the
input electrical machine as a generator to at least partly power
the output electrical machine as a motor; b) determining the
angular position of the crank arms; c) controlling the current in
the input electrical machine so as not to exceed a maximum current
nor fall below a minimum current for the determined angular
position of the crank arms.
2. A method of operating a pedal cycle, the pedal cycle having an
electro-mechanical drive arrangement including an input electrical
machine, an output electrical machine and an input epicyclic gear
set; wherein, of the input epicyclic gear set, a first component is
coupled to be driven by crank arms of the cycle, a second component
is coupled to one of the rotor and stator of the input electrical
machine, the other of the rotor and stator being fixed relative to
the cycle, and the third component is coupled to drive a wheel of
the cycle; the output electrical machine being arranged to be
driven by the or by another wheel of the cycle and to be operated
as a generator; the method including the steps of: a) operating the
output electrical machine as a generator to at least partly power
the input electrical machine as a motor to at least assist in
driving the wheel coupled to the third component; b) determining
the angular position of the crank arms; c) controlling the current
in the input electrical machine so as not to exceed a maximum
current nor fall below a minimum current for the determined angular
position of the crank arms.
3. A method according to claim 1, wherein the arrangement includes
an output epicyclic gear set, a first component thereof being fixed
relative to the cycle, a second component thereof being coupled to
the rotor of the output electrical machine, the stator being fixed
relative to the cycle, and the third component thereof being
coupled to drive the, or the other, wheel of the cycle.
4. A method according to claim 1, wherein the maximum current and
the minimum current are the same.
5. A method according to claim 1, wherein there are a plurality of
maximum and minimum currents for the determined angular position of
the crank arms, and wherein step (c) includes the step of
determining a maximum and minimum current from the plurality
thereof and then controlling the current in the input electrical
machine so as not to exceed this determined maximum current and/or
not fall below this determined minimum current for the determined
angular position of the crank arms.
6. A method according to claim 5, wherein the determining includes
receiving an input from a user indicative of a selected maximum
and/or minimum current and using this to set the determined maximum
current and/or minimum current.
7. A method according to claim 6, wherein the determining further
includes determining the cadence of the crank arms and using this
to set the determined maximum current and or minimum current.
8. A method according to claim 7 and including the step of
consulting a record indicative of how torque output of a cyclist
varies with cadence, and from this obtaining and indication of a
torque that corresponds to the determined cadence, and hence of an
appropriate maximum and minimum current.
9. A method according to claim 1, wherein the maximum and minimum
currents are different at different angular positions of the crank
arms, thereby at least partly taking account of the natural
variation in torque applied by the cyclist to the crank arms over
one cycle, the method including the step of varying the maximum and
minimum currents with angular position of the crank arms
accordingly.
10. A method according to claim 1 and including supplying
substantially all electrical energy generated by one of the input
and output electrical machine to the other of the input and output
electrical machine to operate that other electrical machine as a
motor.
11. A method according to claim 1 and including receiving an assist
input from a user indicating that stored electrical energy should
be supplied to the output electrical machine to supplement
electrical energy supplied thereto and generated by the input
electrical machine; and including supplying stored electrical
energy accordingly in response to receipt of the assist input.
12. A method according to claim 11 and including supplying stored
electrical energy to the output electrical machine regardless of
whether or not electrical energy is being generated by the input
electrical machine.
13. A method according to claim 1, wherein the method includes the
step of controllably supplying electrical power to the output
electrical machine such that that power varies over a cycle of the
crank arms so as to at least reduce the tendency for variation in
power output to the or each driven wheel over a cycle of the crank
arms that results from a variation in power input by the cyclist
over that cycle.
14. A method according to claim 13, wherein the method includes the
step of powering the output electrical machine by discharging the
store of electrical energy over successive cycles of the crank
arms; and/or by storing temporarily electrical energy generated in
one part of the cycle of the crank arms, and using this to power
the output electrical machine in another part of the cycle.
15. A method according to claim 1, wherein the method includes the
step of determining that the bicycle and/or the crank arms are
substantially stationary and, in response thereto, substantially
short-circuiting the input electrical machine.
16. A method according to claim 15, wherein the method includes the
step of maintaining the substantial short-circuiting of the input
electrical machine until the actual current in the input electrical
machine reaches the maximum current.
17. A method according to claim 1, wherein the method includes the
step of operating one or both of the electrical machines as a
generator to retard the pedal cycle.
18. A pedal cycle arranged to carry out a method according to claim
1; or an electronic control unit programmed and operable to carry
out a method according to claim 1; or a computer program having
code portions executable by the electronic control unit that
carries out a method according to claim 1; a record carrier having
thereon or therein a record of a computer-readable instructions
executable to cause the electronic control unit to carry out a
method according to claim 1.
19. The method according to claim 17, wherein the step of operating
one or both of the electrical machines as a generator to retard the
pedal cycle includes operating one or both of the electrical
machine inefficiently.
20. A method according to claim 19, wherein one or both of the
electrical machines are operated inefficiently by shifting the
phase of the current and/or voltage thereof to dissipate generated
electrical energy as heat and thereby retard the pedal cycle.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a national phase of PCT application No.
PCT/GB2010/000249, filed 12 Feb. 2010, which claims priority to GB
patent application No. 0902356.5, filed 12 Feb. 2009; EP patent
application No. 09251183.1, filed 24 Apr. 2009; and EP patent
application No. 09159467.1, filed 5 May 2009, all of which are
incorporated herein by reference.
FIELD
This invention relates to a method of operating a pedal cycle
having an electro-mechanical drive arrangement.
BACKGROUND
There are various forms of pedal cycle. One, conventional, form of
pedal cycle is that which is only ever driven by a cyclist applying
force to the pedals thereof, such cycles sometimes being referred
to as "push bikes". Another, more recent, form of pedal cycle is
the electrically-assisted pedal cycle (EAPC) in which electrical
power is used to assist the efforts of a cyclist pedalling the
cycle. Both conventional pedal cycles and EAPCs may have two, three
or four wheels, and, in some, cases even more. In the present
document, the term "pedal cycle" is used to include both
conventional pedal cycles and EAPCs.
As mentioned, in an EAPC, electrical power is used to assist the
efforts of a cyclist pedalling the cycle. Accordingly, EAPCs
include means for storing electrical energy, such a batteries, and
an electric motor arranged to propel, or at least assist in
propelling, the cycle. The batteries can usually be recharged by
plugging them into a supply of electrical energy, such as an outlet
from a mains supply, and also by recovering energy from motion of
the cycle by way of regenerative braking. The principle of
regenerative braking will be familiar to those skilled in this
field of technology. As a result, the overall effort required by a
cyclist to pedal an EAPC is lower than for a conventional
cycle.
EAPCs can usually be placed into one of two groups. The first group
is that in which the cycle can provide electrical assistance on
demand, at any time, regardless of whether or not the cyclist is
pedalling. Cycles in this group are sometimes referred to as
"e-bikes", and can be thought of as being generally equivalent to
electric mopeds, although one that is generally easier to pedal.
Cycles in the second group only provide electrical assistance when
the cyclist is pedalling. These are sometimes referred to as
"pedelecs".
In most European countries, pedelecs at least are effectively
classified as conventional bicycles and so may be ridden without a
driving license or insurance. In at least the UK, e-bikes are also
classified in this way. There are therefore few barriers to owning
and operating an EAPC.
In recent years, technical advances have been made to the
electro-mechanical drive arrangements and to the associated energy
storage and recovery devices used in EAPCs. These advances have
resulted in EAPCs that can be operated with greater efficiency, and
hence greater ease, by the cyclist.
For all the reasons given above EAPCs are becoming increasing
popular, particularly in some European countries.
A suitable electro-mechanical drive arrangement for driving an EAPC
is described in WO-A1-2006/035215, the contents of which are herein
incorporated in their entirety. For example, this earlier document
describes, with reference to FIG. 2 thereof, an arrangement that
can be mounted to replace the conventional hub of a rear wheel of a
bicycle. The replacement hub contains first and second
motor-generators and first and second epicyclic gear sets. The
arrangement is such that the motor-generators and the epicyclic
gear sets operate to provide a compact drive arrangement combining
(a) a variable transmission ratio between the input from the
cyclist and the output to the driving wheel, with (b) electrical
assistance.
Although various drive arrangements exist for EAPCs, including that
described in WO-A1-2006/035215, the unpredictable nature of how a
cyclist will cycle makes control and operation of such arrangements
problematic. In this respect, a cyclist is very different from an
engine.
An object of at least certain embodiments of this invention is to
provide a method of operating an electro-mechanical drive
arrangement for a pedal cycle similar to that described in
WO-A1-2006/035215.
SUMMARY
According to one aspect of this invention, there is provided a
method of operating a pedal cycle, the pedal cycle having an
electro-mechanical drive arrangement including an input electrical
machine, an output electrical machine and an input epicyclic gear
set; wherein, of the input epicyclic gear set, a first component is
coupled to be driven by crank arms of the cycle, a second component
is coupled to one of the rotor and stator of the input electrical
machine, the other of the rotor and stator being fixed relative to
the cycle, and the third component is coupled to drive a wheel of
the cycle; the output electrical machine being arranged to at least
assist in driving the or another wheel of the cycle when operated
as a motor; the method including the steps of:
a) operating the input electrical machine as a generator to at
least partly power the output electrical machine as a motor;
b) determining the angular position of the crank arms;
c) controlling the current in the input electrical machine so as
not to exceed a maximum current nor fall below a minimum current
for the determined angular position of the crank arms.
By controlling the current in the input electrical machine in this
way, the torque on that machine, which is proportional to current,
is also controlled. As the input electrical machine is coupled to
the crank arms by the second epicyclic gear set, controlling the
torque in the input electrical machine also controls the torque in
the crank arms (the two are proportional), which is the torque that
the cyclist applies. Thus, controlling the current in the input
electrical machine determines the torque which the cyclist
applies.
Controlling the current in this way results in the arrangement
automatically "changing gear". For example, should the cyclist
press on the pedals with more force such that he or she applies
torque that exceeds the torque corresponding to the maximum current
of the input electrical machine for the determined crank position,
the electrical machine "gives way" and so accelerates. This changes
the transmission ratio of the input epicyclic gear set to, in
effect, change into a lower gear. Thus, when the torque that the
cyclist applies exceeds a certain limit, the arrangement
automatically changes down into a lower gear. Thus, the arrangement
automatically changes down in conditions when this is needed, such
as when climbing a hill or accelerating rapidly.
Similarly, should the cyclist press the pedals with less force and
hence apply less torque than the torque that corresponds to the
minimum current of the input electrical machine, the electrical
machine decelerates and resists motion of the crank arms by the
cyclist. This deceleration of the input electrical machine again
changes the transmission ratio of the second epicyclic gear set to,
in effect, change into a higher gear. Thus, when the torque that
the cyclist applies falls below a certain limit, the arrangement
automatically changes up into a higher gear. Thus, the arrangement
automatically changes up in conditions when this is needed, such as
when going down hill or when easing off and approaching a steady
speed from a period of acceleration.
In this way, embodiments of the invention may be used in
conventional pedal cycles and in EAPCs to provide an arrangement
for automatically changing gear.
It will be appreciated by the skilled person that current control
of an electrical machine may be readily accomplished with existing
electrical components. Thus, embodiments of the method can be used
to provide automatic transmission-ratio control in a conventional
pedal cycle and/or in an EAPC in a straightforward and inexpensive
manner. It should also be noted that the use of an epicyclic gear
set in this way provides continuously-variable transmission, rather
than the stepped gearing usual with cycles that often changes gear
unsatisfactorily under heavy loads.
The method may include operating control means to operate the input
electrical machine as a generator and/or to operate the output
electrical machine as a motor and/or to control the current in the
input electrical machine. The control means may include one or more
motor controllers and/or one or more generator controllers.
The arrangement may include an output epicyclic gear set, a first
component thereof being fixed relative to the cycle, a second
component thereof being coupled to the rotor of the output
electrical machine, the stator being fixed relative to the cycle,
and the third component thereof being coupled to drive the, or the
other, wheel of the cycle.
The third component of the input epicyclic gear set may be coupled,
and the output electrical machine may be arranged, to drive and be
driven by one and the same wheel of the pedal cycle. The two may
be, respectively, coupled and arranged to drive and be driven by
different wheels of the cycle
In an embodiment, the first component of the input epicyclic gear
set may be the planetary carrier, the second component thereof may
be the sun gear, and the third component thereof may be the
annulus. Similarly, in an embodiment, the first component of the
output epicyclic gear set may be the planetary carrier, the second
component thereof may be the sun gear and the third component
thereof may be the annulus.
The maximum current and the minimum current may be different
values; they may be the same value. Where they are different
values, this creates a band within which the torque applied by the
cyclist may vary without the arrangement "changing gear", i.e.
varying the transmission ratio. In this way, the arrangement
mimics, at least to some degree, the behaviour of a conventional
geared cycle and so may find favour with some cyclists more used to
such conventional cycles. Where the maximum current and minimum
current are the same, this results in the arrangement varying the
transmission ratio whenever the torque applied by the cyclist
differs from that corresponding to the current drawn from the input
electrical machine. This arrangement can be used to cause the
cyclist to cycle with a torque that is close to, or coincides with,
optimum cycling efficiency.
There may be a plurality of maximum and/or minimum currents for the
determined angular position of the crank arms. Step (c) may include
the step of determining a maximum and/or minimum current from the
plurality thereof and then controlling the current in the input
electrical machine so as not to exceed this determined maximum
current and/or not fall below this determined minimum current for
the determined angular position of the crank arms. The determining
may include receiving an input indicative of a selected maximum
and/or minimum current and using this to set the determined maximum
current and/or minimum current. The determining may include or may
further include determining the cadence of the crank arms and using
this to set the determined maximum current and or minimum current.
For example the method may include consulting a record indicative
of how torque output of a cyclist varies with cadence, and from
this obtaining an indication of a torque that corresponds to the
determined cadence, and hence of an appropriate maximum and/or
minimum current.
The input may be received from input means operable by the
cyclist.
There may be a plurality of selectable pairs of maximum and minimum
currents for the determined angular position of the crank arms.
Where the maximum in one selectable pair is larger than the maximum
in another selectable pair, the minimum in the one pair may also be
larger than the minimum in the other pair. Thus, a plurality of
different bands is created. Where the maximum and minimum currents
are the same, there may be a plurality of singly selectable,
different, currents.
Selecting the maximum and/or minimum currents in this way allows
the cyclist to select the level of torque at which the arrangement
varies the transmission ratio to coincide with his or her personal
preference. Furthermore, by selecting different maxima and/or
minima whilst cycling, without necessarily varying the torque he or
she applies to the crank arms, the cyclist can force the
arrangement to vary the transmission ratio.
The maximum and minimum currents may be different at different
angular positions of the crank arms. This is to take account of the
natural variation in torque applied by the cyclist to the crank
arms over one cycle. The maximum and minimum currents may vary
sinusoidally with angular position of the crank arms. The method
may include the step of varying the maximum and minimum currents
with angular position of the crank arms.
The method may include supplying all electrical energy generated by
the input electrical machine to the output electrical machine for
operating the output electrical machine as a motor.
In this way, a conventional pedal cycle fitted with the
electro-mechanical arrangement may be provided with an arrangement
for automatically changing gear.
The method may include supplying stored electrical energy to the
output electrical machine from a store of electrical energy for
operating the output electrical machine as a motor. The method may
include supplying stored electrical energy in this way to
supplement electrical energy generated from the input electrical
machine and supplied to the output electrical machine. The method
may include receiving an assist input indicating that stored
electrical energy should be supplied to the output electrical
machine to supplement electrical energy supplied thereto and
generated by the input electrical machine; and may include
supplying stored electrical energy accordingly in response to
receipt of the assist input. The method may include operating the
control means to supply stored electrical energy in this way. In
this way, stored electrical energy can be used to assist the
cyclist in propelling the cycle.
The assist input may be received from assist input means operable
by the cyclist.
The assist input may be indicative of one of a plurality of
selectable levels of assistance that is to be provided to the
cyclist. The assist input may be indicative of a factor by which
the power input by the cyclist should be augmented by power
supplied to the output electrical machine by discharging the store
of electrical energy. The method may include discharging the store
of electrical energy and operating the output electrical machine at
least partly thereby, in response to receipt of the assist
input.
The method may only supply stored electrical energy to the output
electrical machine to supplement generated electrical energy, and
may supply substantially no electrical energy to the output
electrical machine, such that the output electrical machine is not
operated as a motor, when no electrical energy is generated by the
input electrical machine. In this way, the cycle operates as a
pedelec.
The method may supply stored electrical energy to the output
electrical machine regardless of whether or not electrical energy
is being generated by the input electrical machine. The method may
do this in response to receiving the assist input or in response to
receiving another input. In this way, the cycle can be operated as
an e-bike. The other input may be a throttle input, variably
indicative of the electrical power that should be supplied to the
electrical machine.
The method may include the step of controllably supplying
electrical power to the output electrical machine such that that
power varies over a cycle of the crank arms. The variation may be
such that it at least reduces the variation in power output to the
or each driven wheel over a cycle of the crank arms, such variation
resulting from a variation in power input by the cyclist over that
cycle. In this way, the power to the output electrical machine is
varied over a cycle of the crank arms to at least partly make up
for the naturally sinusoidally varying input to the arrangement by
the cyclist and such that the cycle performs more smoothly over a
cycle of the crank arms. In doing this the output electrical
machine may be powered by discharging the store of electrical
energy over successive cycles of the crank arms; and/or by storing
temporarily electrical energy generated in one part of the cycle of
the crank arms, and using this to power the output electrical
machine in another part of the cycle. The one part of the cycle may
be a part in which power input by the cyclist is relatively high,
and the other part of the cycle may be a part in which power input
by the cyclist is relatively low. The output electrical machine may
be powered in this way such that there is substantially no
depletion of the store of electrical energy over a complete cycle.
In this way, the method may "iron out" fluctuations in power input.
The control means may arranged accordingly.
The method may include the step of determining that the crank arms
are substantially stationary and, in response thereto,
substantially short-circuiting the input electrical machine in
response thereto. By short-circuiting the input electrical machine
when the crank arms are at rest, the input electrical machine can
be substantially locked such that power input by the cyclist is
transmitted mechanically through the input epicyclic gear set to
the driven wheel, thereby allowing the cyclist to pull smartly away
from rest. The method may include maintaining the substantial
short-circuiting of the input electrical until the actual current
in the input electrical reaches the maximum current. The short
circuit may be maintained for less than half a cycle; it may be
maintained for less than quarter of a cycle; it may be maintained
for between about 10 to 20 degrees of rotation of the crank arms;
it may be maintained for about 15 degrees of rotation.
The method may include operating the input electrical machine
and/or the output electrical machine as a generator to retard the
pedal cycle. Electrical power generated in this way may be used to
recharge the store of electrical energy. The method may include
operating one or both of the electrical machines inefficiently, for
example, by shifting the phase of the current and/or voltage
thereof to dissipate generated electrical energy as heat and
thereby retard the pedal cycle. The method may include operating
the input electrical machine and/or the output electrical machine
as a generator in this way in response to a signal from a brake
input device operable by the cyclist. The brake input device may be
a brake lever. The method may include operating the input and/or
output electrical machine in this way in response to sensing
backwards movement of the crank arms; and optionally, backwards
movement of the crank arms when the crank arms are between 60
degrees and 120 degrees to the vertical when the pedal cycle is on
level ground.
The pedal cycle may be, for example, a conventional pedal cycle in
which drive is only ever provided by a cyclist applying force to
the pedals thereof, such cycles sometimes being referred to as
"push bikes". The pedal cycle may be, for example, an EAPC, such
as, for example, a pedelec or an e-bike. The pedal cycle may have
one, two, three, four or more wheels. The pedal cycle may be a
bicycle (including solo and tandem bicycles), a tricycle, or
conceivably any form of cycle which can be at least partly
propelled by a cyclist pedalling.
According to a second aspect of this invention, there is provided a
method of operating a pedal cycle, the pedal cycle having an
electro-mechanical drive arrangement including an input electrical
machine, an output electrical machine and an input epicyclic gear
set; wherein, of the input epicyclic gear set, a first component is
coupled to be driven by crank arms of the cycle, a second component
is coupled to one of the rotor and stator of the input electrical
machine, the other of the rotor and stator being fixed relative to
the cycle, and the third component is coupled to drive a wheel of
the cycle; the output electrical machine being arranged to be
driven by the or by another wheel of the cycle and to be operated
as a generator; the method including the steps of:
a) operating the output electrical machine as a generator to at
least partly power the input electrical machine as a motor to at
least assist in driving the wheel coupled to the third
component
b) determining the angular position of the crank arms;
c) controlling the current in the input electrical machine so as
not to exceed a maximum current nor fall below a minimum current
for the determined angular position of the crank arms.
In at least certain embodiments of this second aspect, the
electro-mechanical arrangement can be the same as that of at least
certain embodiments of the first aspect, but the input electrical
machine is operated in these embodiments of the second aspect as a
motor and powered by the output electrical machine being operated
as a generator. In similarity with the first aspect, in at least
certain embodiments of this second aspect, the current in the input
electrical machine is controlled in the same way (albeit with that
machine operating as a motor) such that the arrangement
automatically changes gear in the same way. As will be understood
from the description of certain exemplary embodiments hereinbelow,
the electro-mechanical drive arrangement may automatically operate
in accordance with the second aspect on one side of the "node
point" described below, and may operated in accordance with the
first aspect on the other side of the "node point". For example, by
maintaining substantially the same current in the input electrical
machine, as the cyclist accelerates the pedal cycle, operation may
start in accordance with the first aspect, cross the node point,
and then operate in accordance with the second aspect, without
substantially changing that current.
Optional features of the first aspect may also be optional features
of the second aspect.
According to a third aspect of the invention, there is provided
a
pedal cycle arranged to carry out a method as defined
hereinabove.
According to a third aspect of this invention, there is provided
processing means programmed and operable to carry out a method as
defined hereinabove.
According to a fourth aspect of this invention, there is provided a
computer program having code portions executable by processing
means to cause those means to carry out a method as defined
hereinabove.
According to a fifth aspect of this invention, there is provided a
record carrier having thereon or therein a record of a
computer-readable instructions executable to cause processing means
to carry out a method as defined hereinabove.
The record carrier may include storage means. The storage means may
include solid state storage means, such as non-volatile memory. The
storage means may include one or more of ROM, EPROM, EEPROM and
flash memory. The storage means may include an optical and/or
magnetic disk. The record carrier may include an electrical, radio
and/or electromagnetic signal.
BRIEF DESCRIPTION OF THE DRAWINGS
Specific embodiments of the invention will now be described by way
of example only and with reference to the accompanying drawings, in
which:
FIG. 1 shows a pedal cycle in which the invention is embodied;
FIG. 2 shows a sectional view of a wheel hub of the pedal cycle in
which certain components of an electro-mechanical drive arrangement
are housed, the section being taken radially;
FIG. 3 is schematic representation of control means for controlling
operation of the drive arrangement;
FIG. 4 is a flow diagram of steps of one embodiment of a method of
operating the pedal cycle, the steps including steps of a "launch"
routine and an "in-motion" routine;
FIG. 4a is an example of a graph showing the variation with cadence
of torque applied by a cyclist to crank arms of the pedal
cycle;
FIG. 5 is a flow diagram of steps of a modified in-motion routine
of an alternative embodiment of the method;
FIG. 6 is a flow diagram of steps of an assist routine that may
form part of embodiments of the method;
FIG. 7 is a flow diagram of steps of a braking routine of
embodiments of the method;
FIG. 8 is a combined sectional and schematic view of a crank case
of an alternative pedal cycle in which the invention is embodied,
the section being taken radially;
FIG. 9 is a section view of a front hub and a rear hub of another
alternative pedal cycle in which the invention is embodied, the
sections again being radial; and
FIG. 10 is a schematic view of the layout of certain components of
a four-wheeled pedal cycle in which the invention is embodied.
SPECIFIC DESCRIPTION OF CERTAIN EXEMPLARY EMBODIMENTS
Structural Arrangement
FIG. 1 shows an electrically-assisted pedal cycle in the form of a
bicycle 10. The bicycle 10 is similar to a conventional bicycle in
having a steerable wheel 20 at the front and a driveable wheel 30
at the back. The bicycle 10 also has the conventional arrangement
of pedals 40 on crank arms 50 that drive a front toothed cog 60
connected by a chain 70 to a rear sprocket 80, the rear sprocket
being mounted co-axially with the rear wheel 30. However, the
bicycle 10 differs from a conventional bicycle in that the rear
sprocket 80 is not fixedly mounted to the hub 100 of the rear wheel
30 to drive that wheel directly. Instead, the rear sprocket 80
drives certain components of an electro-mechanical drive
arrangement that are housed within the hub 100.
FIG. 2 shows the hub 100 and its contents in detail. These include
a first electrical machine in the form of a first radial-flux
motor-generator 110, a second electrical machine in the form of a
second radial-flux motor-generator 120, a first epicyclic gear set
130 and a second epicyclic gear set 140. For ease of reference, the
second motor-generator 120 and the second epicyclic gear set 140
will be referred to as the "input motor-generator" 120 and "input
epicyclic gear set" 140 (because they are more directly coupled to
the rear sprocket 80); and the first motor-generator 110 and first
epicyclic gear set 130 will therefore be referred to as the "output
motor-generator" 110 and the "output epicyclic gear set" 130.
The arrangement of the input epicyclic gear set and input
motor-generator will firstly be described. The input sprocket 80 is
fixedly mounted to a collar that forms the planetary carrier 142 of
the input epicyclic gear set 140. That planetary carrier 142 is
mounted on bearings 143 for rotation about a rear wheel axle 150
that is fixed to the frame of the bicycle 10. The planet gears 144
are rotatably mounted on the planetary carrier 142 and mesh with a
sun gear 146. The sun gear 146 is fixedly coupled to the rotor 122
of the input motor-generator 120 for rotation therewith, and is
rotatably mounted about the axle 150. The stator 124 of the input
motor-generator is fixedly mounted to the axle 150. The annulus
148, which also meshes with the planet gears 144, is fixed to an
internal wall of the hub 100. As can be seen from FIG. 2, the
planet gears 144 are stepped gears, with the part thereof that
meshes with the annulus 148 being of lesser diameter than the part
thereof that meshes with the sun gear 146.
The arrangement of the output epicyclic gear set 130 and the output
motor-generator 110 will now be described. The planetary carrier
132 of the output epicyclic gear set 130 is fixedly mounted on the
axle 150. The planet gears 134 are rotatably mounted on the
planetary carrier 132 and mesh with the sun gear 136. The sun gear
136 is fixedly coupled to the rotor 112 of the output motor
generator 110 for rotation therewith, and is rotatably mounted
about the axle 150. The stator 114 of the output motor-generator
110 is fixedly mounted to the axle 150. The annulus 138, which also
meshes with the planet gears 134, is fixed to the internal wall of
the hub 100. The planet gears 134 of the output epicyclic gear set
130 are also stepped gears, with the part thereof that meshes with
the annulus 138 being of lesser diameter than the part thereof that
meshes with the sun gear 136.
The hub 100 is rotatably mounted, at one end, on the axle 150 by a
bearing 102 and, at the other end on the collar that is the
planetary carrier 142 of the input epicyclic gear set 140 by a
bearing 104. The hub 100, supports, in the conventional manner,
spokes that in turn support a wheel rim such that the hub can
transmit torque to the rim for driving the bicycle 10.
Thus, the arrangement is very similar to that described in
WO2006/035215 with reference to FIG. 2 of that publication. Indeed,
it is envisaged that each of the arrangements disclosed in that
publication may provide, in alternative embodiments of the present
invention, the electro-mechanical drive arrangement of the bicycle
10 described herein with reference to FIG. 1.
Although, in the present embodiment, both of the epicyclic gear
sets 130, 140 have toothed gears that mesh, it is envisaged that
non-meshing contact-only epicyclic gear sets may be substituted for
these in other embodiments.
Returning to the present embodiment and with reference to FIG. 3,
the bicycle 10 also includes control means 200 that is connected
and arranged to control the input and output motor-generators 110,
120 in response to inputs received from input means. The control
means 200 is in the form of an electronic control unit (ECU) 205, a
battery management unit 207 and two motor-generator controllers:
one of which will be termed the "input controller" 210 and is for
controlling the input motor-generator 130, and the other one of
which will be termed the "output controller" 220 and is for
controlling the output motor-generator 110. The ECU 205 includes a
microprocessor that is programmable and operable to carry out the
steps of a method that embodies this invention. That method will be
described hereinbelow with reference to FIG. 3 and FIG. 5. The ECU
205 is connected to the input controller 210, the output controller
220 and the battery management unit 207 for controlling operation
of those three units.
The input means that provide inputs to the control means 200
includes user input means 250 and a crank speed and position sensor
260. The user input means 250 includes, in this embodiment, a
user-operable power input device and a user-operable brake input
device (none of which is shown). The power input device is arranged
to be operated by a user to indicate generally the power, that is
the rate of working, with which he or she wishes to pedal. The
brake input device is arranged to be operated by the user to
indicate a rate at which the bicycle 10 should be slowed.
In this embodiment, it is envisaged that the power input device is
a user-operable selector that indexes between each of a plurality
of different positions. Examples of such selector switches are
twistable grip-shifts and thumb shifters commonly used in
gear-change mechanisms of conventional bicycles. It is envisaged
that the brake input device may be similar to a conventional brake
lever. However, in the present embodiment, it is envisaged that
electrical versions of such selector switches and of the brake
lever be used such that each is able to product an electrical
signal indicative of its user-selected position. The crank speed
and position sensor 260 is a conventional device that is arranged
to sense the speed and angular position of the crank arms 50 and to
output an electrical signal indicative of this. Each of the input
means is connected and arranged to provide its respective
electrical signal to the ECU 205.
A further output from the control means 200 is connected to an
instrument panel 270.
The battery management unit 207 is connected to electrical energy
storage means in the form of a rechargeable battery 208.
With reference again to FIG. 1, the ECU 205, the input controller
210, the output controller 220 and the battery management unit are
housed within a control housing 90 fitted to the frame of the
bicycle 10. The battery 208 is housed within a battery housing 92
that is also fitted to the frame.
Operation
Operation of the bicycle 10 will now be described. This description
will take the form of a description of the steps of a method
carried out by the ECU 205 in executing instructions contained in a
computer program with which it is programmed.
With reference to FIG. 4, the method begins at step 300 in which
the bicycle speed is sensed. This is done by the ECU 205 sensing
the speed of the output motor-generator 110, the speed of the
output motor-generator 110 being proportional to the speed of the
bicycle 10. The ECU 205 senses the speed of the output
motor-generator 110 by receiving a signal indicative of this from
motor commutation sensors (although, in other embodiments, the
voltage or the frequency of voltage peaks may instead by
measured)
At step 310, the ECU 205 then determines from the speed sensed in
step 310 whether or not the bicycle 10 is stationary. If it is not
(i.e. if the bicycle 10 is moving) then the method executes an
"in-motion" routine 320 that begins with step 321. If the bicycle
is stationary, the method executes a "launch" routine 330 that
begins with step 331. The launch routine 330 will be described
below. Firstly however, the in-motion routine 320 is described.
In-Motion Routine
The in-motion routine 320 begins at step 321 in which the ECU 205
senses the output from the crank position and speed sensor 260 and
determines from that the crank speed with which the cyclist is
pedalling.
The in-motion routine 320 then proceeds to step 322. In this step,
the ECU 205 senses the signal from the power input device, that
signal being indicative generally of the power with which the
cyclist wishes to pedal. As stated, the power input device is
operable by the cyclist to select one from a plurality of settings,
each corresponding generally to a respective power with which he or
she wishes to pedal.
At step 323, the ECU 205 senses the output from the crank position
and speed sensor 260 and determines from that the current position
of the crank arms 50.
The method then proceeds to step 324 in which the ECU 205
determines a current that is to be drawn from the input
motor-generator 120 operating as a generator. It should be
understood that, by controlling the current in the input
motor-generator 120 in this way, the torque on that machine, which
is proportional to current, is also controlled. As the input
motor-generator 120 is coupled to the crank arms 50 by the input
epicyclic gear set 140, controlling the torque in the input
motor-generator 120 also controls the torque in the crank arms 50
(the two torques are proportional), which is the torque that the
cyclist applies to the crank arms 50 through the pedals 40. Thus,
controlling the current in the input motor-generator 120 determines
the force which the cyclist must apply to the pedals 40. In step
324, the ECU 205 controls the current drawn from the input
motor-generator 120 so as to cause the pedals 40 to react against
the cyclist with a force that gives rise to the cyclist pedalling
with the power which the cyclist has indicated she or he wishes to
pedal by the position of the power input device. In doing this, the
ECU 205 makes use of the previously determined crank speed
(determined in step 321) and the previously determined crank
position (determined in step 323) to determine the current as a
function of crank speed and crank position. This will now be
explained in more detail.
Firstly, variation of the current as a function of crank speed is
described. For each user-selectable setting of the power input
device, the ECU 205 has access to a respective graph, or more
precisely to information substantially indicative thereof in the
form of a look-up table, that shows how the torque that a cyclist
typically applies to crank arms 50 of a bicycle varies with crank
speed (or "cadence" as it is sometimes called). An example of one
such a graph is shown in FIG. 4a. As can be seen from FIG. 4a, the
torque tends to reduce with increased cadence (and so it will be
appreciated that such a graph also gives an indication of how the
power output of the cyclist varies with cadence). Each of the
graphs is generally of the same shape as each other, but the graphs
are such that they would be spaced apart along the y-axis, that is
along the torque axis, if shown on the same axes. Thus, each graph
represents a cyclist cycling with different power across the
cadence range. Having previously sensed the input provided by the
power input device, the ECU 205 looks up the graph (or rather the
look-up table) that corresponds to the user-selectable setting of
the power input device indicated by that input. From this, the ECU
205 determines a torque with which the cyclist should pedal. As
already mentioned, torque of the crank arms 50 is directly
proportional to torque in the input motor-generator 120, which is
directly proportional to current in that machine. The ECU 205
therefore applies a simple conversion factor to get a "notional"
current that should be caused to exist in the input motor-generator
120 to give the torque retrieved from the look-up table that
corresponds to the sensed crank speed for the user-selected power
level.
Now, variation of the current as a function of crank position will
be described. There is a natural variation in the force with which
the cyclist presses on the pedals 40 over the crank cycle (for
example, at top-dead-centre and bottom-dead-centre of the crank
cycle the cyclist will exert almost no useful force on the pedals
40). The ECU 205 therefore modifies the "notional" to give an
actual current to be drawn from the input motor-generator 120 that
accounts for this natural variation. This actual current is
constant for the same crank angle in successive crank cycles. Thus,
this gives the same reaction force at the pedals 40 at the same
crank angle in each cycle. The current is, however, varied over
each crank angle sinusoidally with the crank angle. There are
various ways in which this may be done. In the present embodiment,
the ECU 205 applies an algorithm to the notional current to
determine the actual current that varies with crank angle and that
is to be drawn from the input motor-generator 120.
That completes step 324.
At step 325, the ECU 205 controls the input controller 220 such
that the input motor-generator 120 is operated such that current
determined in step 324 exists therein. At least at low bicycle
speeds, this corresponds to operating the input motor-generator 120
as a generator. Step 325 concludes the in-motion routine 320.
Controlling the current in this way results in the bicycle 10
automatically changing the transmission ratio between the crank
arms 50 and the rear wheel. For example, should the cyclist press
on the pedals 40 with more force such that he or she applies torque
that exceeds the torque corresponding to the current drawn from the
input motor-generator 120 for the determined crank position, the
motor-generator "gives way" and so accelerates. This changes the
transmission ratio of the input epicyclic gear set 140 to change to
a lower ratio. Thus, when the torque that the cyclist applies
exceeds a certain limit, the arrangement automatically changes to a
lower ratio. Thus, the arrangement automatically changes down in
conditions when this is needed, such as when climbing a hill or
accelerating rapidly.
Similarly, should the cyclist press the pedals 40 with less force
and hence apply less torque than the torque that corresponds to the
determined current that is to be drawn from the input
motor-generator 120, the motor-generator 120 decelerates and
resists motion of the crank arms 50 by the cyclist. This
deceleration of the input motor-generator 120 again changes the
transmission ratio of the second epicyclic gear set to a higher
ratio. Thus, when the torque that the cyclist applies falls below a
certain limit, the arrangement automatically changes to a higher
ratio. Thus, the arrangement automatically changes up in conditions
when this is needed, such as when going down hill or when easing
off and approaching a steady speed from a period of
acceleration.
By providing the cyclist with several user-selectable settings of
the power input device, each one corresponding to a respective one
of the graphs of torque against cadence, the cyclist can select
generally the power with which he or she wishes to cycle.
Additionally, he or she may change that power whilst cycling so
that he or she can cycle generally harder or more easily.
After the in-motion routine 320, the method executes an assist
routine 340, before returning to step 300. The assist routine 340
will be described further below with reference to FIG. 6. Firstly,
however, the launch routine 330 mentioned above will be
described.
Launch Routine
The launch routine 330 referred to above will now be described.
Should the ECU 205 determine at step 310 that the bicycle 10 is
stationary, the method executes the launch routine 330 and proceeds
to step 331.
At step 331, the ECU 205 senses the signal from the power input
device in the same way as in step 322 of the in-motion routine
320.
At step 332, the ECU 205 senses and determines the current crank
angle in the same way as in step 323 of the in-motion routine
320.
At step 332, the ECU 205 determines the current that should be
drawn from the input motor-generator 120, based on the signal from
the power input device, the current crank angle and on the basis
that the cadence is approximately zero (the graphs referred to
hereinabove of torque against cadence include an indication of the
torque applied by the cyclist at approximately zero cadence), in
the same way as in step 324 of the in-motion routine 320.
The launch routine 330 then proceeds to step 334 in which the ECU
205 controls the input controller 210 to very nearly short-circuit
the first motor-generator 110 (it generally being difficult to
completely short-circuit the first motor-generator 110 because some
current usually would usually need to flow between there and the
input controller 210).
This effective short-circuit quickly builds up a reaction torque in
the input motor-generator 120 against rotation thereof (this build
up happens within about 5 to 10 degrees of crank angle). This
reaction is transmitted through the input epicyclic gear set 140 to
the crank arms 50 and pedals 40 and so gives the cyclist something
to push against in setting off on the cycle. The effective short
circuit tends to lock the input motor-generator 120 such that its
rotor 122 does not rotate when the cyclist applies force to the
pedals 40 and so transmits torque via the crank arms 50, the chain,
the rear sprocket 80, the planetary carrier 142 and the planet
gears 144 to the sun gear 146, which is coupled to the rotor 122.
As a result, the torque applied by the cyclist is transmitted to
the annulus 148, which is coupled to the hub 100. This causes the
hub, and hence the wheel to which it is connected, to rotate;
thereby driving the bicycle forwards from rest.
At step 335, the ECU 205 senses the actual current in the input
motor-generator 120
Step 336 compares the sensed actual current against the current
determined in step 333 and, for as long as the actual current is
less than the determined current, causes the launch routine to
return to step 331 and repeat. When the actual current reaches the
determined current, step 336 causes the ECU 205 to exit the launch
routine 330 and causes the in-motion routine 320 described
hereinabove to start.
Alternative with Max Cadence Control
In a first alternative embodiment, the bicycle is the same as that
10 described hereinabove with reference to FIGS. 1 to 4, save for
the following modifications.
Firstly, the user input means 250 are modified. Instead of having a
user-operable power input device, the input means 250 has a
user-operable torque input device and a user-operable maximum
cadence input device (neither or which are shown) The torque input
device is arranged to be operated by the cyclist to indicate, the
torque that he or she wishes to transmit via the crank arms 50,
that is, to indicate the force with which he or she wishes to
pedal. The maximum cadence input device is arranged to be operated
by the cyclist to indicate, in combination with the torque input
device, the maximum power with which the cyclist wishes to pedal.
Again, it is envisaged that the input devices may be user-operable
selector switches that index between each of a plurality of
different positions.
Operation of this embodiment is generally the same as that
described above with reference to FIG. 4. However, the in-motion
routine 320 described above with reference to FIG. 4 is replaced by
a slightly modified in-motion routine 320'. This modified in-motion
routine 320' will now be described with reference to FIG. 5.
In step 321', the ECU 205 senses and determines the crank speed as
in previously described step 321.
Step 322' is new in this modified in-motion routine 320'. In this
step, the ECU 205 senses the input provided by the torque input
device. This replaces the step of sensing the input provided by the
power input device.
In step 323', the ECU 205 senses and determines the crank angle as
in previously described step 323.
Step 326 is new in this modified in-motion routine 320'. In this
step, the ECU 205 senses the input provided by the maximum cadence
input device.
In step 324', the ECU 205 determines the current to be caused to
exist in the input motor-generator 120. This step is similar to
that 324 previously described, but differs in that no graphs (or
rather look-up tables) of torque against cadence are consulted.
Instead, the ECU 205 determines the "notional" current based only
on the input received from the torque input device, and then
modifies this as previously described as a function of crank angle
to give the actual current to be caused to exist in the input
motor-generator 120 at each crank position. However, in step 324'
the ECU 205 also compares the actual crank speed (i.e. the actual
cadence) against the input received from the maximum cadence input
device. If the actual cadence exceeds the cadence represented by
the input received from the maximum cadence input device, the ECU
205 controls the input controller 210 to reduce the current in the
input motor-generator 120 by a predetermined factor (or in other
embodiments, by a predetermined amount). As will by now be
understood, this reduces the torque in the input motor-generator
120 and the torque reaction transmitted to the cyclist, and so
results in the cyclist to pedalling with lower power output. In
other words, the modified arrangement described in this first
alternative embodiment allows the cyclist to set a preferred
cycling torque and a preferred maximum cycling power. It will be
understood that this modified arrangement also changes ratio
automatically as previously described.
In this alternative embodiment is envisaged that corresponding
changes be made to step 333 of the launch routine 330 to account
for the absence of the look-up tables of torque against
cadence.
Electrical Assistance
In both the first embodiment described above with reference to
FIGS. 1 to 4, and the first alternative embodiment described with
reference to FIG. 5, the bicycle 10 is arranged to provide the
cyclist with electrical assistance. This will now be described.
Firstly, the user input means 250 further includes a user-operable
assist input device and a user-operable brake input device (not
shown). The assist input device is arranged to be operated by the
cyclist to indicate the factor by which the power that he or she
provides to the drive arrangement by pedalling is supplemented with
power from the battery. Again, it is envisaged that the assist
input device is a user-operable selector that indexes between each
of a plurality of different positions.
The method of operation in the first embodiment, and in the first
alternative embodiment, includes an "assist" mode omitted from FIG.
4 and FIG. 5 for clarity, but shown at 340 in FIG. 6. This assist
mode 340 is included in the method after the in-motion mode 320 (or
320') and before the method returns back to step 300.
With continued reference to FIG. 6, the assist mode 340 begins at
step 341 in which the ECU 205 senses the input provided from the
assist input device. As mentioned hereinabove, this input indicates
the factor by which the power that the cyclist provides to the
drive arrangement by pedalling is to be supplemented with power
from the battery 208. In this embodiment, this input can indicate
each of three settings: that no electrical power is to be supplied
from the battery 208 to supplement that provided by the cyclist
(i.e. that no electrical assistance is to be provided), that power
is to be supplied from the battery 208 to match that provided by
the cyclist (e.g. 100% electrical assistance is to be provided),
and that twice as much power is to be supplied from the battery 208
as is provided by the cyclist (e.g. 200% electrical assistance is
to be provided). In other embodiments, the input may be indicative
of each of several different absolute amounts of electrical power
to be supplied from the battery 208.
At step 342, the ECU 205 then determines the power currently being
supplied by the cyclist from a combination of the crank speed
(sensed by sensing the input from the crank speed and position
sensor 260) and the current determined in step 324 (or 324') and
set in step 325 (this current, as mentioned above, is proportional
to the torque in the input motor-generator 120 and hence the torque
applied by the cyclist).
The method then proceeds to step 343 in which the ECU 205 controls
the battery management unit 207 and the output controller 210
accordingly.
Specifically, if the input received from the assist input device
indicates that no electrical assistance is to be provided, then the
ECU 205 controls the battery management unit 207 such that no
electrical power is supplied by the battery 208, and such that the
output controller 210 operates the output motor-generator 110 as a
motor powered solely by the electrical power generated by the input
motor-generator 120. Thus, the rear wheel is driven mechanically
and electro-mechanically purely from power supplied by the cyclist.
The rear wheel is driven mechanically by the cyclist through the
crank arms 50, rear sprocket 80, planetary carrier 142, planet
gears 144 and annulus 148 of the input epicyclic gear set 140 to
drive the hub 100; and electro-mechanically through the crank arms
50, rear sprocket 80, planetary carrier 142, planet gears 144 and
sun gear 146 of the input epicyclic gear set 140 to drive the input
motor-generator 120 as a generator and supply electrical power to
the output motor generator 110 as a motor, which drives the hub 100
through the sun gear 136, planet gears 134 and annulus 138 of the
output epicyclic gear set 130.
If, however, the input received from the assist input device
indicates that electrical assistance should be provided, the ECU
205 controls the battery management unit 207 such that electrical
power is supplied from the battery 208 to the output electrical
machine 110 to supplement that generated by the input electrical
machine 120 and supplied thereto. The ECU 205 operates to supply a
level of electrical power determined by the input received from the
assist input device and the power calculated at step 330 as being
input by the cyclist. In this way, the factor of electrical power
assistance selected by the cyclist is provided. In other respects,
operation is the same as that just described for no electrical
assistance.
Braking
In the embodiments described hereinabove, the bicycle has a brake
input device that is variably operable by the cyclist to produce a
signal indicative of a rate at which the cyclist wishes to brake
the bicycle. The method of each of the described embodiments is
such that the ECU 205 executes a breaking routine, shown at 350 in
FIG. 7, when it receives an input from the brake input device
indicative of the cyclist wishing to brake the bicycle. The braking
routine 350 begins at step 351 with the ECU 205 sensing the input
from the brake input device. At step 352, the ECU 205 determines an
output current that when drawn from the output motor-generator 110
operating as a generator would exert a braking torque on the rear
wheel 30 that would slow the bike at the rate of braking indicated
by the input from the brake input device. At step 353, the ECU 205
controls the output controller 220 such that the output
motor-generator 110 operates as a generator with the current
determined in the previous step drawn therefrom.
In the embodiments described above, the ECU 205 operates the output
controller 220 and the battery management unit 207 such that power
generated by the output motor-generator 110 during braking is used
to recharge the battery 208. In this way, regenerative braking is
provided. Should the battery 208 be fully recharged, the
arrangement operates to connect a resistor (not shown) across the
output motor-generator 110 such that power generated thereby is
dissipated as heat from the resistor. In alternative embodiments,
the ECU 205 operates the output motor-generator 110 and/or the
input motor-generator 120 inefficiently as generators, for example
by shifting the phase of the current and/or voltage such that
rotation of the or each generator is resisted, thereby braking the
rear wheel 30. In such an arrangement, energy is dissipated in the
windings and metal structure (sometimes referred to as the "iron")
or the or each generator 110, 120.
In the embodiments described above, the bicycle includes a
conventional brake on its front wheel.
Free-Wheel Routine
In order to allow the bicycle to free-wheel, the method include a
"free-wheel" routine. This routine is not illustrated, but includes
the steps of the ECU 205 sensing that the crank arms 50 are
rotating at a cadence of less than 10 cycles per minute, and that
the bicycle 10 is moving, and then, in response thereto, ceasing to
cause a current to exist in the input motor-generator 120 and the
output motor-generator 110 for as long as the crank arms 50 rotate
at a cadence of less than 10 cycles per minute. In this way, the
input motor-generator 120 can spin freely, such that no torque is
transmitted back to the cyclist via the crank arms 50 or to the
rear wheel 30 via the input epicyclic gear set 140. Similarly, the
output motor generator 110 and hence the front wheel 20 also spin
freely. Thus, the bicycle 10 can free-wheel.
Push Bike Alternative
In a second alternative embodiment, the bicycle 10 is modified to
omit the battery 208 and the battery management unit 207. Thus, the
modified bicycle (not shown, but similar in other respects to that
10 shown in FIG. 1) does not have an assist mode 340 and so
transmits all power generated by the input motor-generator 120
operating as a generator to the output motor generator 110 to
operate that machine as a motor to assist in driving the bicycle.
Some electrical power may be used to power the control electronics,
but, otherwise, substantially all generated power is used in
driving the modified bicycle. In this way, a conventional bicycle
(sometimes referred to as a "push bike") can be provided with
automatically-changing ratios in a continuously variable
transmission-type arrangement. It will be understood that, as the
modified bicycles in this alternative embodiment omits the battery
208, there is also no regenerative braking to recharge such a
battery in this embodiment.
Back Pedal Braking
In any of the embodiments described hereinabove, the bicycle 10 may
be modified such that it additionally provides for back pedal
braking. Those familiar with pedal cycle technology will understand
that back pedal braking is provided on some bicycles by the
inclusion of a specially adapted rear wheel hub in which components
act to brake the hub when a backwards torque is exerted on the rear
wheel sprocket by the cyclist attempting to pedal backwards with
the cranks generally horizontal. The braking force applied to the
hub is generally dependent on the backwards torque exerted on the
rear wheel sprocket. The modification now described is to provide
such functionality to embodiments of the present invention
electro-mechanically.
The modification includes a "back pedal braking" routine (not
shown) being included in any or all of the methods described
hereinabove. The ECU 205 causes the method to enter this routine
upon detecting backward motion of the crank arms 50 when those arms
are between approximately 60 and 120 degrees from the vertical,
that is, when very approximately horizontal. Upon entering the
routine, the ECU 205 causes the input motor-generator 120 to be
operated as a generator by drawing a current therefrom, such that
the input motor-generator 120 is driven via the input epicyclic
gear set 140 by rotation of the rear wheel 30, such that rotation
of the rear wheel 30 is thereby resisted by the input
motor-generator 120. Thus, a braking torque is applied to the rear
wheel 30. Operating the input motor-generator 120 as a generator in
this way to apply a braking torque to the rear wheel 30 also causes
a torque to be transmitted back, via the crank arms 50, to the
cyclist to oppose the backward pedalling. This reaction against the
cyclist gives feedback that the bicycle 10 is being braked.
The back pedal braking routine further includes the ECU 205
increasing the current drawn from the input motor-generator 120 in
response to sensing further backward movement of the crank arms 50.
It is envisaged that the current drawn, and hence the braking
torque applied, increase to a maximum over approximately 10 degrees
of crank arm movement. The maximum braking torque applied is
limited approximately to that at which the rear wheel 30 tends to
lock and skid.
In a further modification, it is envisaged that the back pedal
braking routine includes the ECU 205 operating the output
motor-generator 110 as a generator in the same way as it operates
the input motor-generator 120 as a generator in this routine,
thereby applying a braking torque to the front wheel 20. In such a
further modification, the brake input device referred to above
would be omitted.
As with the regenerative braking described hereinabove, power
generated by the input motor-generator 120 (and by the output
motor-generator 110) when operated in this way in response to
back-pedalling can be used to recharge the battery 208.
Sporty Back Pedal Braking
In any of the embodiments described above, the bicycle may include
an alternative to the form of back pedal braking just described. In
this alternative, the ECU 205 causes the method to enter a "sporty
back pedal braking" routing upon detecting that the crank arms 50
are moving backwards. In this routine, the ECU 205 causes the input
motor-generator 120 to operate as a generator with a predetermined
current drawn therefrom. As already described, this tends to brake
the rear wheel 30. By pedalling backwards, the cyclist provides
torque that helps to turn the input motor-generator 120 as a
generator and that also helps to brake the rear wheel 30. Thus, the
bicycle is braked and electrical power is generated that can be
used to recharge the battery 208. It will be appreciated that the
current drawn from the input motor-generator 120 in this routine is
of opposite direction from that caused to exist in the in-motion
routine described hereinabove with reference to FIG. 4.
Anti-Lock Braking
In any of the embodiments described above, the bicycle may be
further modified to include an anti-lock braking system (ABS). In
such a modification, the ECU 205 senses the speed of the input
motor generator 120 and/or the speed of the output motor-generator
110 by conventional means. In response to determining deceleration
of one or both of the motor-generators 110, 120 above a
predetermined rate, or sudden stopping of one or both
motor-generator 110, 120, the ECU 205 operates to reduce the
current drawn from the or each motor-generator that is decelerating
too rapidly or, as the case may be, that stops suddenly. The method
may include the ECU 205 increasing the relevant current again once
it has determined that the or each motor-generator 110, 120 is no
longer decelerating above the predetermined rate or, as the case
may be, is no longer stopped.
Traction Control
It is similarly envisaged that in one or more embodiments, the ECU
205 may operated to control the current the input motor-generator
and/or the output motor-generator to provide traction control to
the front and/or rear wheel.
Node Point
Reference is made hereinabove to a "node point". At lower speeds,
the input motor-generator 120 is operated as a generator, with the
current determined in step 324 (or 324') drawn therefrom.
Accordingly, the output motor-generator 110 is operated as a motor
and powered at least partly by the input motor-generator 120. As
the cyclist pedals faster and causes the bicycle to accelerate and
the arrangement to, as described, automatically change the
transmission ratio, the input motor-generator 120 slows down, even
though (or rather because) the current drawn therefrom remains the
same. As the cyclist continues to accelerate the bicycle, at one
point of operation the input motor-generator 120 stops and then
begins to turn in the other direction, with the current therein
still maintained constant. With the input motor-generator now
rotating in the opposite direction, but with the current therein
still controlled to be the same, the input motor-generator 120 is
now operating as a motor. Accordingly as the input motor-generator
120 is connected to the output motor-generator 110, that output
machine 120 is now operating as a generator. The point at which the
input motor-generator 120 changes direction is the "node point".
This is a natural phenomenon of the embodiments described above and
happens automatically as a result of the ECU 205 controlling the
first controller 210 to maintain a constant current in the input
electrical machine 110. It allows the arrangement to provide a
broader range of transmission ratios, that is of different "gears"
automatically selectable by the arrangement. In the method of
operation described hereinabove with reference to FIGS. 4 to 7, the
input motor-generator 120 is mainly described as operating as a
generator (as is the case when the cyclist is operating the bicycle
at speeds below the node point) for simplicity of explanation.
However, it will now be understood, that the method of current
control described hereinabove results in the input motor-generator
120 operating as a motor and the output motor-generator 110
operating as a generator above the node point.
Alternative Packaging
The control means 200 described hereinabove with reference to FIG.
3, and the methods of operation described hereinabove with
reference to FIGS. 4 to 7, may be used to operate similar, but
differently configured, electro-mechanical arrangements in other
pedal cycles.
For example, the control means and method may be used to control a
first alternative arrangement such as that 400 shown in FIG. 8. In
this first alternative arrangement, an input motor-generator 474
and an output motor-generator 476 are provided, together with an
epicyclic gear set, in the crank case of a bicycle. Two crank arms
450 are joined to each other by a crank axle 452. The crank axle
452 is coupled to and rotates a planetary carrier 471 with planet
gears 472 thereon. The planet gears 472 mesh with a radially-inner
set of teeth on a sun gear 473, a radially-outer set of teeth on
that same sun gear 473 meshing with a pinion gear 478 coupled to
the rotor of the input motor-generator 474. The planet gears 472
also mesh with a radially-inner set of teeth on an annulus gear
475, a radially-outer set of teeth on the annuls gear 475 meshing
with another pinion gear 477 coupled to the rotor of the output
motor-generator 476. The annulus gear 475 is coupled to drive the
usual large toothed cog 460 that is concentric with the crank axle
452, but which in this arrangement is not coupled to the crank arms
450. The toothed cog 460 receives a chain (not shown) for driving a
sprocket mounted on the rear wheel in the conventional way. In
other words, the electro-mechanical configuration of this first
alternative arrangement is like that shown in and described in and
with reference to the drawing of European Patent Application No.
09251183.1, it being envisaged that the present method may be used
to control such an arrangement.
Alternatively, the control means and method may be used to control
a second alternative arrangement such as that 500 shown in FIG. 9.
This is similar to the first arrangement described hereinabove with
reference to FIG. 2, but differs in that the input motor-generator
120 and input epicyclic gear set 140 only are maintained in the hub
100 of the rear wheel 30, with the output motor-generator 110 and
output epicyclic gear set 130 being mounted in the hub of the front
wheel 20. Other than that, the arrangement 500 is substantially the
same as that previously described.
FIG. 10 shows another arrangement 600 in which control is provided
in substantially the same way for a four-wheeled pedal cycle having
two pairs of crank arms 610 with pedals thereon, each pair of crank
arms coupled to a respective large toothed cog in the conventional
manner. Each rear wheel includes one of the hub-mounted
arrangements described hereinabove with reference to FIG. 2. A
driveshaft is provided between the two arrangements to couple
together the planetary carriers 142 of the two input epicyclic gear
sets 140. Two sprockets are provided on and coupled to the
driveshaft, each to receive and be driven by a respective chain
coupled to a respective one of the large toothed cogs. Providing a
hub-mounted arrangement such as this in each rear wheel removes the
need for a differential, the inclusion of which in four-wheeled
pedal cycles, especially those that are electrically assisted, has
proved problematic.
Use as Exercise Cycle
It is envisaged that any of the embodiments described above may be
arranged for use as a stationary exercise pedal cycle. For such
use, the pedal cycle would be supported with its rear wheel or
wheels fixed and pedalled by a cyclist to rotate the or each input
motor-generator. It is envisaged that such a pedal cycle would
include a user-operable control to determine the current drawn from
the or each input motor-generator and hence the resistance against
which the cyclist pedals. It is envisaged that electrical power
generated by the cyclist in using the pedal cycle in this way be
used to recharge the battery.
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